The invention relates to the regulation of groups of power sources, which may be uniform such as solar-array sources, or may be a mixture between solar-array sources as well as other power sources. The common element is that the invention involves limiting the amount of individual power source voltage regulation allowing all but one of the active devices to be operating at either a maximum or optimum level of operation.
Prior art conventional satellite power systems employ linear-shunt regulators that are terminated across their distributed solar-array sources as a means to regulate the system bus voltage. For stiff bus voltage regulation within an operating load range, a number of linear-shunt devices are turned-off to fully enable their respective solar array currents to charge the output bus voltage and load circuit. Concurrently, other linear-shunt devices are turned-on to completely shunt their respective array currents from the output bus while other shunt devices are linearly controlled to partially shunt some of their respective array currents. Partial and/or complete shunting of the array current to the power return path results in satellite heating due to unnecessary thermal stress on the shunt devices. By adding a tapped terminal for each array source and placing its respective shunting device between the tapped and power return terminals, the shunt-device voltage as well as the device's thermal stress is further reduced. However, thermal stress remains significant and continues to degrade spacecraft reliability. These solar array channels may have a dedicated number of shunt devices that are sequentially turned off as load demand increases. The solar array channels that belong to the partially turned-on and completely turned-off shunt devices supply sufficient flow of power to regulate the bus voltage and fulfill load demand. To insure sufficient bus voltage near end-of-life (EOL), the regulated bus voltage is usually set significantly below the beginning-of-life (BOL) peak-power voltage of each solar array channel, resulting in poor utilization of available power from the activated solar array channels.
This invention involves is a highly efficient power and control architecture employing distributed dc-dc converters, which sequentially regulate power flows from independent solar-array sources to a common load. The invention will significantly reduce power dissipation in power electronic circuits that are used to process the solar array power. The system will maximally utilize the available power of the activated array channels as load demand increases. There should be significantly reduced thermal stress on the array channels that participate in maximum power transfer. The system achieves the regulated bus voltage while all but one of the activated array channels are in maximum power tracking mode. It allows power expansion capability through parallel-connection of Commercial-off-the-Shelf (COTS) dc-dc converters. The system has applicability to other types of conventional and renewable energy sources (utility grid, fuel cells and wind generators).
The sequentially-controlled solar array power system offers a certain sequence of maximum utilization of the distributed solar array sources. Every solar array source will be assigned its own turn (or priority) to participate in the output voltage regulation while the previously activated array sources have already operated in their maximum power tracking modes. This sequential control scheme also allows different type of distributed power sources to work together in a proper order of control priority to minimize the long-term cost of obtaining electrical energy. Furthermore, the control priority (or sequence of power channel activation) for each power channel can be changed with respect to others to best suit the economical and/or practical circumstances that may be different for various geographical areas where the same power system may be differently located. Furthermore, the proposed invention offers the complete bypass (or take-over) of all internal output voltage regulation control loops existing among COTS converters connected in parallel. In general, these control loops in COTS converters cannot be assumed to be identical. The proposed invention employs only one common voltage regulation controller that has only one voltage reference and deliver only one common error signal to control all the power channels.